1. Field of the Invention
The present invention relates to a vertical injection molding machine for molding parts by opening and closing a mold in the vertical direction, and specifically relates to a vertical injection molding machine capable of preventing components movable in the up-down direction provided on the vertical injection molding machine from falling due to their own weight.
2. Description of the Related Art
In the prior art, a two-station vertical injection molding machine has been used where two lower molds attached to a turn table are moved by rotating the turn table respectively to a position opposing to a single upper mold to allow opening and closing of the mold, and opening and closing the mold in the vertical direction. In such vertical injection molding machine for clamping the upper mold with multiple lower molds, a fabrication method is adopted for integrally molding a metallic insert component with resin, where a metallic component used for insert molding is assembled to the lower mold arranged on the opposite side of the lower mold subjected to mold clamping during the mold clamping process for molding parts, and after the component is assembled, the turn table is rotated to a given position to subject the lower mold having the metallic component assembled thereto and the upper mold to mold clamping, wherein injection and filling of molten resin to a cavity of the clamped mold is performed by lowering an injection unit arranged above the upper mold and having an injection nozzle attached to a tip (lower end) of the injection unit to the upper mold, and in that state, injection and filling of molten resin to the mold cavity is carried out by driving an injection screw. The driving of the injection screw is performed using a drive source such as a motor via a pulley, a drive belt or the like.
Regarding the prior art technique mentioned above, patent Document 1 (Japanese Patent Laid-Open Publication No. 2008-105185) discloses a vertical injection molding machine, wherein patent document 1 provides a vertical injection molding machine having a toggle-type mold clamping device that drives a movable platen in a direction for opening and closing a mold with respect to a fixed platen using an electric motor as the drive source, wherein a driven pulley attached to a ball screw for driving the toggle-type mold clamping device is prevented from rotating inversely by having projections of a stopper engage with the teeth of the driven pulley so as to prevent the movable platen from falling.
Patent document 2 (Japanese Patent No. 3953395) discloses an art of engaging claws of a stopper with the teeth of a driven pulley having teeth so as to prevent rotation of an output shaft when power supply to an electric motor is stopped in a molded object take-out machine.
Patent document 3 (Japanese Patent Laid-Open Publication No. 2010-189088) discloses an elevator emergency brake device, wherein an elevator in a stopped state can be prevented from moving due to abnormality by having an engagement member engage with an opening formed on a sheave rotated by the up-down movement of the elevator.
The vertical injection molding machine disclosed in patent document 1 teaches an art for preventing a movable platen from falling when the timing belt is disconnected, but normally, the timing belt is not disconnected when the vertical injection molding machine is at a stopped state and often disconnected when the timing belt is rotated along with the operation of the vertical injection molding machine and a large load is applied on the timing belt, so that if the timing belt is disconnected when the driven pulley rotated around the timing belt is rotated, the attempt to speedily engage the projection on the stopper to the teeth of the driven pulley will cause the stopper to be snapped by the rotation of the driven pulley and it will not be possible to promptly prevent the movable platen from falling by the stopping of rotation, whereas patent document 2 discloses an art of reliably preventing movement of the pulley by engaging a stopper to the pulley in the stopped state when the device is stopped by shutting down power supply, but similar to patent document 1, it is difficult to have the stopper engage with the teeth on the outer circumference of the pulley while the pulley is rotating.
The art disclosed in patent document 3 relates to inserting an engagement member to the opening of a sheave at a stopped state so as to reliably prevent the sheave from moving, but for example, in order to engage an engagement member to the sheave during rotation, the impact caused when the engagement member contacts the sheave may damage the engagement member, a member retaining the engagement member, the sheave or a member retaining the sheave, and since the diameter of the opening of the sheave is greater than the diameter of the engagement member, it is substantially difficult to retain the sheave in the static state.
The vertical injection molding machine where the mold is opened and closed in the vertical direction has a mold open/close mechanism for moving a movable mold up and down with respect to a fixed mold, an injection drive unit capable of up-down movement which is moved downward when injecting and filling molten resin to a cavity of the mold, and an injection unit capable of up-down movement which is equipped with the injection drive unit and lowered when performing nozzle touch, wherein since these components fall by their own weight when the operation of the vertical injection molding machine is stopped, they may disturb or cause injury of operators and the like during maintenance and checkup of the vertical injection molding machine.